This application claims the priority of German patent document 197 05 273.8 filed Feb. 12, 1997, the disclosure of which is expressly incorporated by reference herein.
The invention relates to an intake system for an internal-combustion engine.
An intake system for an internal-combustion engine having an intake pipe which is arranged between an air filter and a throttle device and in which an air flow sensor or air mass sensor is arranged is known, for example, from "Bosch Technische Unterrichtung", Motor Manaqement Motronic 08.93. In order to achieve, in the case of such an intake system, a measuring signal of the air flow or air mass sensor which has a high measuring precision, flow conditions are required in the area of the air flow or air mass sensors which are as uniform as possible over the whole rotational speed range of the internal-combustion engine. Resonance vibrations which occur within the intake system affect, among other influence factors, the flow conditions at this air flow or air mass sensor. If additional control flaps are used in an intake system of this type for an adaptation to different operating conditions, this leads to further influences on the flow conditions which affect the quality of the measuring signal. In the case of intake systems of this type, occurring measuring errors or measuring inaccuracies because of strong air pulsations in the intake pipe are therefore compensated by a pulsation correction in the analysis unit of the measuring signal.
From German Patent Document DE-A-34 16 950, an intake system for an internal-combustion engine is known in the case of which a resonance container is arranged in parallel to the intake pipe between the air filter and the throttle device. This resonance tube has a first connection with the intake pipe just behind the air filter and can be coupled once more with the intake pipe in the proximity of the throttle device by way of a controllable opening. An intake system of this type increases power by a better utilization of the dynamic effects within the intake system and reduces the intake noise.
In contrast, the present invention is based on the object of improving an intake system for internal-combustion engines of the above-mentioned type such that the quality of the measuring signal of the air flow or air mass sensor is improved. In this case, disturbing influences as the result of non-uniform flow conditions in the area of the air flow or air mass sensor are to be reduced so that a subsequent correction of the measuring signal will not be necessary or will be required only to a very minor extent.
This and other objects have been achieved according to the present invention by providing an intake system for an internal-combustion engine having an intake pipe which extends between an air filter and a throttle device, and having an air flow or air mass sensor which is inserted in the intake pipe at a distance D1 from the air filter and at a distance D2 from the throttle device, wherein a Helmholtz resonator is coupled to the intake pipe proximate the air flow or air mass sensor and is tuned to the resonance frequency of the intake pipe occurring during operation of the internal-combustion engine, a distance d of the Helmholtz resonator from the air flow or air mass sensor being less than 0.5.times.D1 or 0.5.times.D2.
This and other objects have also been achieved according to the present invention by providing a method of arranging a Helmholtz resonator in an intake system having an intake pipe extending between an air filter and a throttle device, and an air flow or air mass sensor arranged in the intake pipe at a distance D1 from the air filter and at a distance D2 from the throttle device, said Helmholtz resonator being tuned to the resonance frequency of the intake pipe, said method comprising: coupling the Helmholtz resonator to the intake pipe at a distance d from the air flow or air mass sensor, wherein the distance d is less than 0.5.times.D1 and is less than 0.5.times.D2.
By coupling a Helmholtz resonator tuned to the resonance frequency occurring in the intake pipe during the operation of the internal-combustion engine to the intake pipe in the proximity of the air flow or air mass sensor, a very precise and uniform measuring signal will be obtained if the distance of the Helmholtz resonator from the air flow or air mass sensor, as a function of the installation position, is smaller than half the distance of the air mass sensor either from the air filter or from the throttle device. By positioning the Helmholtz resonator in the direct proximity of the air flow or air mass sensor, the influence of resonance vibrations within the intake pipe on the measuring signal can clearly be reduced so that a subsequent correction will not be necessary or will be required only to a very minor extent.
If the distance between the connection of the Helmholtz resonator to the intake pipe and the air flow or air mass sensor is selected such that it is greater than or equal to 1.5 times the diameter of the resonator connection, the quality of the measuring signal will clearly be improved again because the influence of the vibrations which may form in the resonator connection is very slight.
Furthermore, the quality of the measuring signal generated in the air flow or air mass sensor will clearly be improved if the coupling of the Helmholtz resonator to the intake pipe is situated in the area of a vibration loop of the resonance frequency of the intake pipe occurring in the operation of the internal-combustion engine.
A particularly uniform measuring signal is achieved if the coupling of the Helmholtz resonator to the intake pipe is arranged in the area of the first vibration loop of the resonance frequency of the intake pipe occurring in the operation of the internal-combustion engine, the distance of the vibration loop being greater than or equal to 1.5 times the diameter of the resonator connection.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.